Internal blow out preventers typically include a tubular having upper and lower seats mounted therein and rotatably receiving a ball. Together these components form a ball valve for checking pressure and preventing blow outs in high pressure drilling applications. During operation, the seats have surfaces that contact portions of the external surface of the ball. These contacted portions of the ball experience wear due to prolonged contact with the seats and can fail over time due to extended wear.
To improve the durability of the ball valve a protective coating is often added to the external surface of the ball where it contacts the seats. The juncture of the central opening of the ball and the external surface of the ball creates a sharp/vulnerable edge. Since the protective coating extends from the external surface of the ball up to this vulnerable edge, but not into the central opening of the ball, exposure of this vulnerable edge to high velocity drilling mud and periodic hydrostatic testing of the internal blow out preventer valve at pressures up to 16,000 psi, as required by some drilling systems, often leads to the coating being peeled back or stripped away starting at this vulnerable edge, causing the internal blow out preventer to fail.
The seats also include central openings aligned with the central opening of the ball to allow drilling mud to flow therethrough. The manufacturing tolerances of some internal blow out preventers result in the inside diameter of the ball being smaller than the inside diameter of the upper seat. This exposes the juncture of the external surface of the ball and the central opening of the ball and increases the probability of the coating being stripped from the ball.
Accordingly, a need exists for an improved internal blow out preventer with increased durability.